Association Between Epiretinal Membrane Geometry and Metamorphopsia

Purpose: To investigate the association between the geometric characteristics of epiretinal membranes (ERM) and metamorphopsia in patients with ERM. Methods: This retrospective study included 48 eyes with idiopathic ERM. En face swept-source optical coherence tomography and corresponding fundus photographs were used to determine the ERM extent. Geometric characteristics of ERM (centroid location, circularity, area, and perimeter) were quantified using ImageJ software. Inter-observer agreement for centroid-fovea distance was evaluated using intraclass correlation coefficient (ICC). A multivariable logistic regression model was constructed including centroid-fovea distance, central macular thickness (CMT), and ectopic inner foveal layer (EIFL) presence after collinearity diagnostics. Metamorphopsia was evaluated using M-CHARTS (M(avg) > 0). Results: Metamorphopsia was documented in 36 of 48 eyes (75.0%). Centroid-fovea distance was significantly greater in eyes with metamorphopsia than in those without (0.938 ± 0.540 mm vs. 0.449 ± 0.203 mm, p < 0.001). Perimeter was significantly greater (p = 0.022) and circularity was significantly lower (p = 0.008) in eyes with metamorphopsia, whereas ERM area and BCVA did not differ. Inter-observer reproducibility for centroid-fovea distance was good (ICC = 0.770). In multivariable logistic regression, longer centroid-fovea distance (per 0.1-mm increase; adjusted OR = 2.40, 95% CI: 1.27-4.57, p = 0.007) and greater CMT (adjusted OR = 1.02, 95% CI: 1.00-1.04, p = 0.035) were independently associated with metamorphopsia. The ROC curve demonstrated good discriminative ability (AUC = 0.833). However, centroid-fovea distance was not correlated with metamorphopsia severity (R² = 0.026, p = 0.269). Conclusions: The centroid-foveal distance is significantly associated with the presence, but not the severity, of metamorphopsia in eyes with ERM. These findings suggest that spatial displacement of the tractional center relative to the foveal center (FC) may contribute to the pathogenesis of metamorphopsia, whereas its severity is likely determined by additional microstructural and biomechanical factors. Our results provide further insight into the anatomical-functional correlation in eyes with ERM.